Disc biasing apparatus with a split-finger biasing tool for a data storage device

ABSTRACT

A biasing tool with a main body portion, for biasing a disc relative to a central axis of rotation of a motor hub by steps for biasing the disc adjacent the motor hub. The biasing tool includes; a first and second biasing finger each having a protruding disc engagement region, each biasing finger extending from the main body portion, and an attachment aperture confined within the main body portion accommodating alignment of the biasing tool relative to the disc. The steps include selectively engaging the disc with a disc engagement region of the first or second biasing finger, and aligning a center of rotation of an annular servo track written on the disc with the central axis of rotation of the motor hub by biasing the disc adjacent the motor hub, which forms a common rotational axis for the motor hub and the annular servo track.

FIELD OF THE INVENTION

This invention relates generally to the field of magnetic data storagedevices, and more particularly, but not by way of limitation, to a discbiasing tool with a split-finger biasing tool for biasing a discrelative to a central axis of a motor hub of a data storage device.

BACKGROUND

A key component of a computer system is a device, (such as a datastorage device DSD) to store data. The most basic parts of a DSDincludes an information storage disc (disc) that is rotated, an actuatorthat moves a read/write head (head) to various locations over datatracks of the disc, and electrical circuitry used for encoding data sothat the data can be successfully retrieved and written to the discsurface. Servo tracks are provided on the disc surface to fosterpositional control of the head relative to the disc surface during dataexchange operations. A microprocessor controls most of the operations ofthe DSD including exchanging data between the computer system and theDSD.

Among the challenges associated with data storage device assemblyprocesses are; cost effective techniques for attaining a substantialcoexistence between an axis of rotation of a motor hub rotating thedisc, assuring a center of rotation for the servo tracks, and minimizingimbalanced rotation of the disc. Improved control over imbalancedrotation of the disc and substantial attainment of the coexistencebetween the rotational center of the servo tracks and the axis ofrotation of a motor hub enhances attainment of increased storagecapacity of the DSD.

As such, challenges remain and a need persists for cost effectivetechniques for rotational balance control and substantial coexistencebetween an axis of rotation of a motor hub and a center of rotation forthe servo tracks of a DSD.

SUMMARY OF THE INVENTION

In accordance with preferred embodiments, a method, apparatus, andcombination are provided for aligning an annular servo track with acenter of rotation offset from a central axis of rotation of a motor hubby biasing a storage disc (disc) (upon which the annular servo track iswritten) adjacent the motor hub. Alignment of the center of rotation ofthe annular servo track with the central axis of rotation of the motorhub forms a common rotational axis for the motor hub and the annularservo track, as well as substantially offsetting a rotational imbalanceof the discs for data storage devices having a plurality of discs.

In one embodiment, the biasing apparatus preferably has a biasing toolwith a main body portion, at least a first and second biasing fingerwherein each biasing finger has a proximal end and extends from the mainbody portion. The biasing tool further preferentially includes a discengagement region protruding from a distal end of each biasing fingerand an attachment aperture confined within the main body portion, foraccommodating alignment of each disc alignment region relative to thedisc.

In another embodiment of the present invention, the preferred steps ofthe method includes: providing the motor hub supporting a disc having anannular servo track with a center of rotation written on the disc offsetfrom a central axis of rotation of the motor hub; aligning a biasingtool (preferably having at least a first and second biasing finger)adjacent the disc; and selecting a disc engagement region of one of thebiasing fingers for engagement with the disc.

The preferred method steps continue with imparting a bias force on thedisc with the selected engagement region, which aligns the center ofrotation of the annular servo track with the central axis of rotation ofthe motor forming a common rotational axis, for the motor hub and theannular servo track.

A further embodiment of the present invention includes a data storagedevice preferably comprising, a disc biased adjacent a motor hub by thebiasing apparatus executing the preferred steps of the method.

These and various other features and advantages that characterize theclaimed invention will be apparent upon reading the following detaileddescription and upon review of the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cut-away top plan view of a data storage device(DSD) with a disc aligned to a motor hub of the DSD by a preferredembodiment of a biasing apparatus of the present invention.

FIG. 2 is a top plan view of a plurality of annular servo tracks writtenon the disc of FIG. 1.

FIG. 3 is a partial cut-away, cross-sectional elevational view of thepreferred embodiment of the biasing apparatus of the present invention.

FIG. 4 is a partial cut-away, cross-sectional elevational view of abiasing tool of the biasing apparatus of FIG. 3.

FIG. 5 is a top plan view of a preferred embodiment of the biasing toolof FIG. 4.

FIG. 6 is a side elevational view of the preferred embodiment of thebiasing tool of FIG. 5.

FIG. 7 is an end elevational view of the preferred embodiment of thebiasing tool of FIG. 5.

FIG. 8 is a perspective view of the preferred embodiment of the biasingtool of FIG. 5.

FIG. 9 is a top plan view of an alternate preferred embodiment of thebiasing tool of FIG. 4.

FIG. 10 is a side elevational view of the alternate preferred embodimentof the biasing tool of FIG. 9.

FIG. 11 is an end elevational view of the alternate preferred embodimentof the biasing tool of FIG. 9.

FIG. 12 is a perspective view of the alternate preferred embodiment ofthe biasing tool of FIG. 9.

FIG. 13 is a top plan view of another preferred embodiment of thebiasing tool of FIG. 4.

FIG. 14 is a side elevational view of the preferred embodiment of thebiasing tool of FIG. 13.

FIG. 15 is an end elevational view of the preferred embodiment of thebiasing tool of FIG. 13.

FIG. 16 is a perspective view of the preferred embodiment of the biasingtool of FIG. 13.

FIG. 17 is a partial cut-away, cross-sectional elevational view of thebiasing tools of the biasing apparatus of FIG. 3 prior to interactionwith each disc of FIG. 1.

FIG. 18 is a partial cut-away, cross-sectional elevational view of thebiasing tools of the biasing apparatus of FIG. 3 engaging discs of FIG.1.

FIG. 19 is a partial cut-away, cross-sectional elevational view of thebiasing tools of the biasing apparatus of FIG. 3 engaging all discs ofFIG. 1.

FIG. 20 is a partial cut-away, cross-sectional elevational view of thebiasing tools of the biasing apparatus of FIG. 3 aligning all discs ofFIG. 1.

FIG. 21 is a partial cut-away, cross-sectional elevational view of thebiasing tools of the biasing apparatus of FIG. 3, disengaging from alldiscs of FIG. 1, post alignment of all discs of FIG. 1.

FIG. 22 is a flowchart of preferred method steps for aligning the discof FIG. 1 to the motor hub of FIG. 1.

DETAILED DESCRIPTION

Referring now to the drawings, FIG. 1 provides a top plan view of a datastorage device (DSD) 100. The DSD 100 includes a base deck 102cooperating with a top cover 104 (shown in partial cut-away) to form asealed housing for a mechanical portion of the DSD 100, referred to as ahead-disc assembly (HDA) 106.

A spindle motor assembly (motor) 108 rotates a number of data storagediscs (disc) 110 with a magnetic recording surface (surfaces) 111 at asubstantially constant operational speed. An actuator assembly(actuator) 112 supports and rotates a number of read/write heads (heads)114 into a data exchange relationship adjacent the surfaces 111, whencurrent is applied to a coil 116 of a voice coil motor (VCM) 118. A headsuspension 120 provides a predetermined spring force on the head 114 tomaintain the proper data exchange relationship between the head 114 andthe disc 110 during operation of the DSD 100. Additionally, the headsuspension 120 serves to connect the head 114 with an actuator arm 122of the actuator 112.

During operation of the DSD 100, the actuator 112 moves the heads 114into the data exchange relationship with the disc 110, i.e., theactuator 112 moves the heads to data tracks 124 on the surfaces 111 towrite data to and read data from the disc 110. When the DSD 100 isdeactivated, the actuator 112 positions the heads 114 adjacent a homeposition 126, and the actuator 112 is confined by latching a togglelatch 128.

Command, control, and interface electronics for the DSD 100 are providedon a printed circuit board assembly 130 mounted to the HDA 106. Duringdata transfer operations, a preamplifier/driver (preamp) 132 attached toa flex circuit 134 conditions read/write signals conducted by the flexcircuit 134 between the printed circuit board assembly 130 and the heads114.

In a preferred embodiment, the disc 110 is clamped adjacent a motor hub136 of the motor 108 by a disc clamp 138. The disc clamp 138 assuresthat the disc 110 remains in a fixed position, relative to the motor hub136, while the motor 108 rotates the motor hub 136 during operation ofthe DSD 100. Additionally, the disc 110 in a preferred embodiment isbiased adjacent the motor hub 136, in a predetermined direction, justprior to completing installation of the disc clamp 138 onto the motorhub 136. In a preferred embodiment, biasing the disc 110 adjacent themotor hub 136, aligns a plurality of annular servo tracks (not shown)written on the disc 110.

FIG. 2 shows a preferred embodiment of the plurality of annular servotracks 140; having a center of rotation 142 offset from a rotationalcenter 144 of the disc 110. The center of rotation 142 of the pluralityof annular servo tracks 140 is confined within a mounting aperture 146of the disc 110, and aligning between the rotational center 144 of thedisc 110 in an index feature 148. The index feature 148 is adjacent anouter diameter 150 of the disc 110, and the mounting aperture 146 isconfined within an inner diameter 152 of the disc 110.

FIG. 3 shows a preferred embodiment of a biasing apparatus 154 of thepresent invention having a biasing tool support structure 156. Thebiasing apparatus 154 provides a plurality of motion generating means158. In a preferred embodiment, the plurality of motion generating means158 are flow controlled pneumatic cylinders. However, one skilled in theart will readily recognize; the motion provided by the plurality ofmotion generating means 158 may be accomplished by a number of alternatedevices such as linear motors, worm gears, rack and pinion arrangements,stepper motors, or any alternate motion generating device.

Preferably, each of the plurality of motion generating means 158 isattached to a pusher block 160, in which the pusher block 160 supports abiasing tool 162 (also referred to herein as a “split-finger” biasingtool 162). Each biasing tool 162 provides at least two biasing fingerssuch as 164 and 166 with a disc engagement region 168.

In a preferred embodiment, the biasing tool support structure 156 israised or lowered, relative to the motor hub 136 supporting theplurality of discs 110, to position each disc engagement region 168 ofthe biasing tool 162 relative to a corresponding disc of the pluralityof discs 110, and one of the plurality of motion generating means 158operates to engage or disengage the disc engagement region 168, withwhich a disc of the plurality of discs 110 corresponds.

Preferentially, each biasing finger, such as 164 or 166, independentlyinteract with its corresponding disc of the plurality of discs 110, toassure each disc of the plurality of discs 110 responds only to the discengagement region 168 of one of the biasing fingers, such as 164 or 166.Each biasing finger of the plurality of biasing fingers, such as 164 or166, corresponding to each one of the plurality of discs 110, isolatesinteraction between the discs 110, which are simultaneously respondingto an interaction with their corresponding biasing finger.

In other words, when biasing each disc of the plurality of discs 110,each disc 110 is individually biased, and a simultaneous biasing of theother discs of the plurality of discs 110 does not influence theindividual behavior of any of the discs 110.

If a biasing tool provides only one biasing finger, such as 164 or 166,but includes at least two disc engagement regions 168, attainment ofproperly biased discs 110 may be difficult, due to variability betweenthe discs 110. Variability of either the outer diameter 150 or the innerdiameter 152 (both of FIG. 2), or both, may lead to non-attainment ofproperly biased discs 110. For example, a mismatch in outer diameters150 of a number of discs of the plurality of discs 110 may lead to discsamong the plurality of discs 110 with smaller diameters failing to bedisplaced by a sufficient amount to attain a complete biasing.Therefore, failing to align the center of rotation 142 (of FIG. 2) ofthe plurality of annular servo tracks 140 (of FIG. 2) with a centralaxis of rotation 170 of the motor hub 136 to form a common rotationalaxis, performance requirements of the DSD 100 (of FIG. 1) may beunattained, or a substantial offsetting of rotational imbalance of thediscs 110 of the DSD 100 may not be achieved.

By biasing each of the plurality of discs 110 in a predetermineddirection, rotational imbalance of the discs of the DSD 100 issignificantly reduced, and in a number of instances, the rotationalimbalance is eliminated. For example, for a DSD 100 with a pair of discs110, each of the pair of discs 110 is biased along a common line, butbiased in opposing directions toward the central axis of rotation 170 ofthe motor hub 136. For a DSD 100 with three discs 110, the predetermineddirection for biasing each disc 110 is toward the central axis ofrotation 170 of the motor hub 136, but rather than the bias force beingapplied to each disc 110 along a common line, the bias force is appliedalong lines separated by 120 degrees.

FIG. 4 shows a bias finger flex aperture 172 provided by the biasingtool 162, which defines the biasing tool 162 as a split-finger biasingtool 162. The biasing finger flex aperture 172 accommodates slightdimensional variations between each of the plurality of discs 110 duringa biasing procedure. It will be noted that the dimensions of the biasingfinger 164 is different than the biasing finger 166. The dimensions ofthe biasing finger 164 and the biasing finger 166 are selected to meetattainment of a common predetermined bias force, as illustrated by aforce vector 174. The bias force is specific to both the configurationof a DSD and the process selected for producing that particular DSD. Thedimensional characteristics of the biasing finger flex aperture 172 isdetermined by an amount of flex each biasing finger of the biasing tool162 undergoes, to assure that only the predetermined bias forceillustrated by the force vector 174 is imparted on each disc 110 duringthe biasing procedure, and to preclude interaction between the biasingfingers 164 and 166.

FIGS. 5, 6, 7, and 8 are preferably viewed together. Collectively, FIGS.5, 6, 7, and 8 illustrate one of the plurality of biasing tools 162 ofthe biasing apparatus 154 (of FIG. 3). The biasing tool (collectivelyillustrated by FIGS. 5, 6, 7, and 8) is configured to accommodate a topdisc and a bottom disc of a four disc stack of a HDA (such as HDA 106 ofFIG. 1).

FIG. 5 shows an attachment aperture 176 confined by a main body portion178 of the biasing tool 162. The attachment aperture 176 accommodatesalignment of each disc alignment region of the biasing tool 162 with thedisc 110 (of FIG. 1) of the HDA 106, with which the disc 110corresponds.

FIGS. 9, 10, 11, and 12 are preferably viewed together. Collectively,FIGS. 9, 10, 11, and 12 illustrate another of the plurality of biasingtools 162 of the biasing apparatus 154 (of FIG. 3). The biasing tool 162(collectively illustrated by FIGS. 9, 10, 11, and 12) is configured toaccommodate any two adjacent discs of a disc stack of a HDA (such as HDA106 of FIG. 1).

FIGS. 13, 14, 15, and 16 are preferably viewed together. Collectively,FIGS. 13, 14, 15, and 16 illustrate yet another of the plurality ofbiasing tools 162 of the biasing apparatus 154 (of FIG. 3). The biasingtool 162 (collectively illustrated by FIGS. 13, 14, 15, and 16) isconfigured to accommodate an outer two of any three adjacent discs of adisc stack of a HDA (such as HDA 106 of FIG. 1).

It will be noted, that any configuration of the biasing tool 162 may beadjusted to accommodate a disc of a HDA (such as HDA 106 of FIG. 1)consisting of a single disc. For data storage devices (such as DSD 100of FIG. 1) that utilize a single disc 110 that incorporates theplurality of annular servo tracks 140 having their center of rotation142 offset from the rotational center 144 of the disc 110 (as shown byFIG. 3), biasing the single disc 110 is a preferential process for theHDA 106 to undergo.

FIGS. 17, 18, 19, 20, and 21 are advantageously viewed together. Each ofthe FIGS. 17, 18, 19, 20, and 21 are illustrative of a step in thebiasing process. FIG. 17 shows the alignment of each of the discengagement regions 168 with a disc of the plurality of discs 110 withwhich they correspond.

FIG. 18 shows a first engagement of a number of the discs 110 of theplurality of discs 110, by a number of the disc engagement regions 168,during the biasing process.

FIG. 19 shows engagement of the remaining discs 110 of the plurality ofdiscs 110, with the remaining disc engagement regions 168, during thebiasing process.

FIG. 20 shows the position of each disc of the plurality of discs 110resulting from the final position of each disc engagement region 168,during the biasing process.

FIG. 21 shows disengagement of each of the disc engagement regions 168from engagement with each of the plurality of discs 110, and the biasingtools 162 awaiting extraction by the biasing apparatus 154 fromalignment with the plurality of discs 110.

FIG. 22 shows a preferred biasing method 200 for biasing a disc (such as110) adjacent a motor hub (such as 136) beginning at start step 202 andcontinuing at process step 204. At process step 204, the motor hub witha central axis of rotation (such as 170) supporting the disc isprovided. The disc preferentially includes an annular servo track (suchas 140) with a center of rotation (such as 142) offset from the centralaxis of rotation of the motor hub.

At process step 206, a biasing tool (such as 162) preferentiallyprovides at least a first biasing finger (such as 164) and a secondbiasing finger (such as 166), which is aligned adjacent the disc. Atprocess step 208, a disc engagement region (such as 168) of one of theplurality of biasing fingers is selected for engagement with the disc.

The preferred biasing method 200, preferentially continues at processstep 210 with a bias force (such as illustrated by force vector 174)imparted on the disc with the selected engagement region. The bias forcealigns the center of rotation of the annular servo track with thecentral axis of rotation of the motor, thereby forming a commonrotational axis for the motor hub and the annular servo track. Thepreferred biasing method 200 concludes at end process step 212.

Accordingly, in preferred embodiments, the present invention is directedto a biasing apparatus (such as 154), a method (such as 200) of biasinga disc (such as 110) adjacent a motor hub (such as 136), and a datastorage device (such as 100) that includes the disc biased adjacent themotor hub by means for biasing a disc adjacent a motor hub, using stepsfor biasing a disc adjacent a motor hub.

In accordance with preferred embodiments, a method, apparatus, andcombination are provided for aligning an annular servo track (such as140) with a center of rotation (such as 142) offset from a central axisof rotation (such as 170) of a motor hub by biasing the disc (upon whichthe annular servo track is written) adjacent the motor hub. Alignment ofthe center of rotation of the annular servo track with the central axisof rotation of the motor hub forms a common rotational axis for themotor hub and the annular servo track, along with substantiallyoffsetting a rotational imbalance of the discs for data storage deviceshaving a plurality of discs.

The biasing apparatus preferably has a biasing tool (such as 162) with amain body portion (such as 178), at least a first and second biasingfinger (such as 164, 166), wherein each biasing finger has a proximalend and extends from the main body portion. The biasing tool furtherpreferentially includes a disc engagement region (such as 168)protruding from a distal end of each biasing finger, and an attachmentaperture (such as 176) confined within the main body portionaccommodates alignment of each disc alignment region relative to thedisc.

The preferred steps of the method included: providing the motor hub,supporting a disc having an annular servo track with a center ofrotation written on the disc, offset from a central axis of rotation ofthe motor hub (such as shown by process step 204); aligning a biasingtool preferably having at least a first and second biasing fingeradjacent the disc (such as shown by process step 206); and selecting adisc engagement region of one of the plurality of biasing fingers forengagement with the disc (such as shown by process step 208).

The preferred method steps continue with imparting a bias force (such asillustrated by force vector 174) on the disc with the selectedengagement region, which aligns the center of rotation of the annularservo track with the central axis of rotation of the motor forming acommon rotational axis, for the motor hub and the annular servo track.

The present invention further includes the data storage devicepreferably comprising the disc biased adjacent the motor hub by thebiasing apparatus executing the preferred steps of the method.

It is to be understood that even though numerous characteristics andadvantages of various embodiments of the present invention haven't beenset forth in the foregoing description, together with details of thestructure and functions of various embodiments of the invention, thisdisclosure is illustrative only, and changes may be made in detail,especially in matters of structure and arrangement of parts within theprinciples of the present invention to the full extent indicated by thebroad general meaning of the terms in which the appended claims areexpressed. For example, the particular elements may vary depending onthe particular application of the biasing apparatus with a split-fingerbiasing tool, while maintaining substantially the same functionalitywithout departing from the scope and spirit of the present invention. Inaddition, although the preferred embodiment described herein is directedto a biasing apparatus with a split-finger biasing tool for a datastorage device, it will be appreciated by those skilled in the art thatthe teachings of the present invention can be applied to other systemswithout departing from the scope and spirit of the present invention.

1. A biasing apparatus comprising a biasing tool having a main bodyportion supporting a first and second independently cantilevered biasingfinger, each biasing finger advancing a disc relative to a central axisof rotation of a hub by imparting a substantially equal bias force onthe disc.
 2. The biasing apparatus of claim 1, in which each biasingfinger comprises: a proximal end adjacent the main body and extends fromthe main body portion in a first direction; a disc engagement regionprotruding in a second from a distal end of each biasing finger; and anattachment aperture confined within the main body portion accommodatingalignment of each disc alignment region relative to the disc.
 3. Thebiasing apparatus of claim 2, in which the biasing tool is a pluralityof biasing tools, and in which the disc is a plurality of discs, whereineach disc of the plurality of discs corresponds to the disc engagementregion of one of the biasing fingers of the plurality of biasing tools,and in which each disc responds independently to an interaction with thebias finger with which it corresponds, and wherein each discindividually responds to a simultaneous interaction of the plurality ofdisc with the plurality of biasing finger.
 4. The biasing apparatus ofclaim 3, in which each disc comprises: a substantially uniform inner andouter diameter; a mounting aperture confined within the inner diameter;a rotational axis within the mounting aperture equidistant from eachpoint along the inner diameter; a data region between the outer diameterand the inner diameter; an index feature adjacent the outer diameter;and a plurality of substantially concentric servo tracks written in thedata region, in which the plurality of concentric servo tracks has acenter of rotation offset from the rotational axis, wherein the centerof rotation is confined within the mounting aperture and positionedbetween the index feature and the rotational axis.
 5. The biasingapparatus of claim 4, in which each disc further comprises an outerdiameter portion adjacent the index feature, wherein each outer diameterportion interacts with the disc engagement region of the biasing fingerwith which the disc corresponds.
 6. The biasing apparatus of claim 5, inwhich the hub is a motor hub, and in which each biasing finger imparts asubstantially equal biasing force on the outer diameter portion of thedisc with which it corresponds, during interaction between each outerdiameter portion and the disc engagement region of the biasing fingerwith which the disc corresponds, wherein the biasing force imparting onthe disc substantially aligns the center of rotation of the servo trackswith the central axis of rotation of the motor hub.
 7. The biasingapparatus of claim 3, in which each biasing finger extends from the mainbody portion in substantially a same direction, and in which the dischas an outer diameter portion and a rotational axis, and further inwhich the second biasing finger is in line with and offset from thefirst biasing finger, wherein the first biasing finger is normal to theouter diameter portion of the disc and positioned between the secondbiasing finger and the outer diameter portion of the disc.
 8. Thebiasing apparatus of claim 7, in which the hub is a motor hub, and inwhich the outer diameter portion of the disc engages the engagementregion of the first biasing finger, wherein the bias force imparted onthe disc by the first biasing finger during interaction between theouter diameter portion of the disc and the first biasing fingermisaligns the rotational axis of the disc relative to the central axisof rotation of the motor hub.
 9. The biasing apparatus of claim 7, inwhich the hub is a motor hub, and in which the outer diameter portion ofthe disc engages the engagement region of the second biasing finger,wherein the bias force imparted on the disc by the first biasing fingerduring interaction between the outer diameter portion of the disc andthe first biasing finger misaligns the rotational axis of the discrelative to the central axis of rotation of the motor hub.
 10. Thebiasing apparatus of claim 2, in which the biasing tool is a pluralityof biasing tools, the disc is a plurality of discs, and in which eachbiasing finger of each of the plurality of biasing tools extends insubstantially a same direction from the main body portion of the biasingtool associated with each biasing finger, wherein each disc of theplurality of discs corresponds to and interacts with a biasing finger ofone of the plurality of biasing tools, and wherein each biasing fingeris configured to impart a substantially equal biasing force on the discwith which it interacts.
 11. The biasing apparatus of claim 10, in whicheach disc of the plurality of discs has an outer diameter portion and arotational axis, and in which the second biasing finger of each of theplurality of biasing tools is in line with and offset from the firstbiasing finger of each biasing tool, wherein the first biasing finger isnormal to the outer diameter portion of the disc of the plurality ofdiscs with which it interacts, and positioned between the second biasingfinger and the outer diameter portion of the disc of the plurality ofdiscs with which the second biasing finger interacts.
 12. The biasingapparatus of claim 11, in which the hub is a motor hub, and in whicheach outer diameter portion of each disc of the plurality of discsengages the engagement region of the biasing finger with which itinteracts, wherein the bias force imparted by each biasing fingerinteracting with the outer diameter portion of the disc with which itcorresponds misaligns the rotational axis of the disc relative to thecentral axis of rotation of the motor hub.
 13. The biasing apparatus ofclaim 12, in which each misaligned rotational axis of each disc of theplurality of discs is misaligned in a predetermined direction from thecentral axis of rotation of the motor hub.
 14. The biasing apparatus ofclaim 13, in which the predetermined direction of misalignment betweeneach disc of the plurality of discs and the central axis of rotation ofthe motor hub substantially offset a rotational imbalance of theplurality of discs.
 15. The biasing apparatus of claim 2, in which thedisc comprises: a substantially uniform inner and outer diameter; amounting aperture confined within the inner diameter; a rotational axiswithin the mounting aperture equidistant from each point along the innerdiameter; a data region between the outer diameter and the innerdiameter; an index feature adjacent the outer diameter; and a pluralityof substantially concentric servo tracks written in the data region, inwhich the plurality of concentric servo tracks has a center of rotationoffset from the rotational axis, wherein the center of rotation isconfined within the mounting aperture and positioned between the indexfeature and the rotational axis.
 16. The biasing apparatus of claim 15,in which the disc further comprises an outer diameter portion adjacentthe index feature, wherein the diameter portion interacts with the discengagement region of the biasing finger with which the disc corresponds,and in which the second biasing finger is in line with and offset fromthe first biasing finger, wherein the first biasing finger is normal tothe outer diameter portion of the disc and positioned between the secondbiasing finger and the outer diameter portion of the disc.
 17. Thebiasing apparatus of claim 16, in which the hub is a motor hub, and inwhich the outer diameter portion of the disc engages the engagementregion of the first biasing finger, wherein the bias force imparted onthe disc by the first biasing finger during interaction between theouter diameter portion of the disc and the first biasing fingersubstantially aligns the center of rotation of the servo tracks with thecentral axis of rotation of the motor hub.
 18. The biasing apparatus ofclaim 16, in which the hub is a motor hub, and in which the outerdiameter portion of the disc engages the engagement region of the secondbiasing finger, wherein the bias force imparted on the disc by thesecond biasing finger during interaction between the outer diameterportion of the disc and the second biasing finger substantially alignsthe center of rotation of the servo tracks with the central axis ofrotation of the motor hub.
 19. A method for biasing a disc adjacent ahub by steps comprising: providing a motor hub with a central axis ofrotation, the motor hub supporting a disc having an annular servo trackwith a center of rotation offset from the central axis of rotation ofthe motor hub; aligning a biasing tool having at least a first andsecond biasing finger adjacent the disc; selecting a disc engagementregion of one of the at least first and second biasing fingers forengagement with the disc; and imparting a bias force on the disc withthe selected engagement region, which aligns the center of rotation ofthe annular servo track with the central axis of rotation of the motorforming a common rotational axis for the motor hub and the annular servotrack.
 20. A data storage device comprising a disc biased adjacent amotor hub by means for biasing a disc adjacent a hub through steps forbiasing a disc adjacent a hub.